Typescript：如何在实例成员属性（mixin）中使用方法装饰器？

Posted 2023-03-13

【中文标题】Typescript：如何在实例成员属性（mixin）中使用方法装饰器？

【英文标题】：Typescript: how to use a method decorator in an instance member property (mixin)?

【发布时间】：2021-06-16 10:03:09

【问题描述】：

背景

我们已经实现了这样的混合（简化）：

export type Constructor<I> = new (...args: any[]) => I;

export interface IBaseService<T = any> 
  create: (data: any) => Promise<T>;


export function BaseService<T>(entity: Constructor<T>): Type<IBaseService<T>> 
  class BaseServiceHost implements IBaseService<T> 
    public repository: Repository<T>;

    create(data: DeepPartial<T>): Promise<T> 
      const newResource = this.repository.create(data);
      return this.repository.save(newResource);
    

  
  return BaseServiceHost;

现在我的服务扩展 BaseService 如下：

@Injectable()
export class ResponseService extends BaseService(ResponseEntity) 
  private readonly respondentService: RespondentService;
  private readonly surveyService: SurveyService;

  create = async (data: ResponseInput): Promise<ResponseEntity> => 
    const respondent = await this.respondentService.findByNaturalKey(data.respondentKey);
    const survey = await this.surveyService.findById(data.surveyId);
    return super.create( respondent, survey, ...data )
  ;

...这很好用。

PS.：create 现在必须是一个属性，否则我会收到以下错误：

Class 'IBaseTenantService<ResponseEntity>' defines instance member property 'create',
but extended class 'ResponseService' defines it as instance member function.

问题

create 方法（现在是属性），需要方法装饰器Transactional()， 但是建设

  @Transactional()  // <--- error here
  create = async (data: ResponseInput): Promise<ResponseEntity> => 
    const respondent = await this.respondentService.findByNaturalKey(data.respondentKey);
    const survey = await this.surveyService.findById(data.surveyId);
    return super.create( respondent, survey, ...data )
  ;

给出以下错误：

The return type of a property decorator function must be either 'void' or 'any'.
  Unable to resolve signature of property decorator when called as an expression.

问题

如何在create 属性中使用Transactional()？解决方法？

【问题讨论】：

@Transactional 来自typeorm-transactional-cls-hooked 还是什么？

@Micael_Levi，是的。没错。

【参考方案1】：

这听起来可能很愚蠢，但你试过吗：

  @Transactional()
  async create(data: ResponseInput): Promise<ResponseEntity> 
    const respondent = await this.respondentService.findByNaturalKey(data.respondentKey);
    const survey = await this.surveyService.findById(data.surveyId);
    return super.create( respondent, survey, ...data )
  ;

?

【讨论】：

@Micael_Levi，我不能使用这个结构的原因是它引发了错误Class 'IBaseTenantService<ResponseEntity>' defines instance member property 'create', but extended class 'ResponseService' defines it as instance member function.